Brookfield Glass Company Insulator, Used by Postal Telegraph-Cable Company, 1882-1889

Insulators--made of poor electrical conductors such as glass, ceramic, plastic, or composite materials--help make electric power and communication transmission lines safe. They isolate wires from utility poles, transmission towers, and buildings--structures that are made of conductive materials that could cause signal degradation, power loss, fire, or pose a shock hazard if the lines touched them.